Fix ForEach variable typing issues

[markwpearce]

Fixes the issue where the loop variable in a for each statement might be randomly untyped.
Remove caching for array default types
Fixes not added unresolved array default types to the list of unresolved symbols for re-validation

Eg:

• in FileA, we do for loop with collection of interface.
• in FileB, we change the type of the thing in that interface
• must edit FileA to see the diagnostics show up (or get fixed)

Fixes: #1466